Class

class Node:
    def __init__(self):
        self.l = None
        self.r = None
        self.feature = None
        self.threshold = -1
        self.answer = None

    def H(self, X):
        # ЭНТРОПИЯ
        c = Counter(X)
        s = 0
        for v in c.values():
            p = v / len(X)
            s += math.log(p) * p
        return -s


    def Q(self, X, Xl, Xr):
        # ФУНКЦИЯ ПОТЕРЬ
        return self.H(X) - len(Xl) / len(X) * self.H(Xl)  - len(Xr) / len(X) * self.H(Xr)


    def is_stop(self, y):
        return len(Counter(y).keys()) <= 1

    def fit(self, X, y):
        if self.is_stop(y):
            self.answer = Counter(y).most_common()[0][0]
            return

        max_q = -1
        max_feature = None
        max_threshold = -1

        for feature in X.columns:
            for val in np.unique(X.values):
                left_cond = X[feature] <= val
                right_cond = X[feature] > val

                q = self.Q(y, y[left_cond], y[right_cond])
                if q > max_q:
                    max_q = q
                    max_feature = feature
                    max_threshold = val

        self.feature = max_feature
        self.threshold = max_threshold
        print(self.feature, self.threshold)

        self.l = Node()
        self.r = Node()
        left_cond = X[self.feature] <= self.threshold
        right_cond = X[self.feature] > self.threshold
        self.l.fit(X[left_cond], y[left_cond])
        self.r.fit(X[right_cond], y[right_cond])